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NGC 1068: No change in the mid-infrared torus structure despite X-ray variability

López-Gonzaga, N. and Asmus, D. and Bauer, F. E. and Tristram, K. R. W. and Burtscher, L. and Marinucci, A. and Matt, G. and Harrison, F. A. (2017) NGC 1068: No change in the mid-infrared torus structure despite X-ray variability. Astronomy and Astrophysics, 602 . Art. No. A78. ISSN 0004-6361. doi:10.1051/0004-6361/201629600.

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Context. Recent NuSTAR observations revealed a somewhat unexpected increase in the X-ray flux of the nucleus of NGC 1068. We expect the infrared emission of the dusty torus to react on the intrinsic changes of the accretion disk. Aims. We aim to investigate the origin of the X-ray variation by investigating the response of the mid-infrared environment. Methods. We obtained single-aperture and interferometric mid-infrared measurements and directly compared the measurements observed before and immediately after the X-ray variations. The average correlated and single-aperture fluxes as well as the differential phases were directly compared to detect a possible change in the structure of the nuclear emission on scales of ~2 pc. Results. The flux densities and differential phases of the observations before and during the X-ray variation show no significant change over a period of ten years. Possible minor variations in the infrared emission are ≲6%. Conclusions. Our results suggest that the mid-infrared environment of NGC 1068 has remained unchanged for a decade. The recent transient change in the X-rays did not cause a significant variation in the infrared emission. This independent study supports previous conclusions that stated that the X-ray variation detected by NuSTAR observations is due to X-ray emission piercing through a patchy section of the dusty region.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Asmus, D.0000-0003-0220-2063
Bauer, F. E.0000-0002-8686-8737
Matt, G.0000-0002-2152-0916
Harrison, F. A.0000-0003-2992-8024
Alternate Title:NGC 1068: No change in the mid-IR torus structure despite X-ray variability
Additional Information:© 2017 ESO. Article published by EDP Sciences. Received 29 August 2016; Accepted 5 October 2016; Published online 19 June 2017. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 294.B-5017 and 093.B-0177 and on data obtained from the ESO Science Archive Facility. The authors thank the anonymous referee for the thoughtful and helpful comments. We also thank the ESO Director’s Discretionary Time Committee for accepting the observations of NGC 1068 few weeks after detecting an increase in the nuclear X-ray flux. This work was based on observations with ESO telescopes at the La Silla Paranal Observatory under programme ID: 294.B-5017, 093.B-0177, 089.B-0099, 080.B-0928, 076.B-0743. N. López-Gonzaga was supported by grant 614.000 from the Nederlandse Organisatie voor Wetenschappelijk Onderzoek and acknowledges support from a CONACyT graduate fellowship. F. E. Bauer acknowledges support from CONICYT-Chile (Basal-CATA PFB-06/2007, FONDECYT Regular 1141218, “EMBIGGEN” Anillo ACT1101), and the Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. L. Burtscher is supported by a DFG grant within the SPP 1573 “Physics of the interstellar medium”.
Group:Astronomy Department
Funding AgencyGrant Number
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)614.000
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)UNSPECIFIED
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1141218
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoIC120009
Deutsche Forschungsgemeinschaft (DFG)SPP 1573
Subject Keywords:galaxies: nuclei – galaxies: Seyfert – techniques: high angular resolution – radiation mechanisms: thermal – galaxies: active
Record Number:CaltechAUTHORS:20170928-131501960
Persistent URL:
Official Citation:NGC 1068: No change in the mid-infrared torus structure despite X-ray variability N. López-Gonzaga, D. Asmus, F. E. Bauer, K. R. W. Tristram, L. Burtscher, A. Marinucci, G. Matt and F. A. Harrison A&A, 602 (2017) A78 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81901
Deposited By: Tony Diaz
Deposited On:28 Sep 2017 20:58
Last Modified:15 Nov 2021 19:46

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